A new study (pdf) by the Society for New Communications Research (SNCR) has found that the percentage of Fortune 500 companies that have public-facing corporate blogs have increased. Now 81 (16%) of the corporations listed on the 2008 Fortune 500 have a corporate blog which has been updated with a new post in the past 12 months. Three of the top five corporations (Wal-Mart, Chevron and General Motors) have blogs while Exxon/Mobil and Conoco Philips do not.

This is up from 14.8% of Fortune 500 companies found in a study (see below) by Burson-Marsteller (where I work) a year ago. But it still a significantly lower percentage than the Inc. 500 (the fastest-growing, private companies in the US), of which 39% have external blogs.

The industry with most blogging corporations was “Computer Software, Peripherals, Office Equipment” with 8 companies followed by Telecommunications (5) and Food Production, Services and Drug Stores (5). The study also showed that the adoption was greater among the largest companies, 38% among the top 100, compared to 10% among 400-500.

Mere than 90% of the Fortune 500 blogs take comments, have RSS feeds andtake subscriptions and 23 companies (28%) linked to a corporate Twitter account.

More corporation on the Fortune 500 are blogging than among the largest Nordic listed companies. A study I did with my colleagues last fall showed that only 9.1% of the corporations on the Large Cap list (the largest listed companies in Sweden, Norway, Denmark and Finland) had external corporate blogs. White paper here (pdf).